Mix warm water, instant yeast, and sugar in a small bowl and let it sit for 5 minutes.
Mix all-purpose flour and salt in the bowl of a stand mixer. Add water-yeast-sugar mixture and olive oil and knead for 5-10 minutes at low speed until you have a smooth dough.
Grease a large bowl with 1 tsp olive oil, place the dough in it, cover with a damp kitchen towel, and let it rise in a warm place for 1 hour until doubled in size.
Meanwhile, mix olive oil, garlic, and herbs for the topping in a small bowl and set aside.
Punch the dough to deflate and place it on a with parchment paper lined baking tray. Stretch and flatten into a rectangle. Push all your fingers a few times deep into the dough for the typical focaccia look. Cover with a damp kitchen towel, and let it rise for another 30 minutes.
Preheat the oven to 450°F (230°C). Spread with the topping and sprinkle with sea salt flakes (optional). Bake if for 10-15 minutes until golden brown. → Turn 180° in the halftime to allow an even browning.
Notes
Keeps fresh: Focaccia does taste best when fresh. Freeze leftovers.
Freeze: Cut the focaccia in small pieces, place them in a zip bag and freeze for up to 3 months. Defrost for 5-10 minutes in the preheated oven (390°F/200°C).
Variations: Omit the garlic or only use rosemary and olive oil for a change.